This invention relates to a valve. The valve is particularly intended for use in the dispensing of beverages that are mixed at the point of sale from a concentrate and a diluent and although not limited to such use, it will for convenience be described further below with specific reference to the dispensing of such beverages.
Beverages that are mixed at the point of sale require accurate metering of the concentrate, e.g. syrup, and the diluent, which is usually plain or carbonated water. It is, therefore, an object of the present invention to provide a valve, and a beverage dispenser incorporating the valve, through which desired ratios can be accurately and reliably metered at an economic cost.
Accordingly in one aspect the invention provides a valve comprising a housing having an inlet and an outlet for a first fluid and an inlet and an outlet for a second fluid, a reciprocatable piston in a central chamber into and from which the inlets and outlets respectively lead, the piston being movable reciprocably between a first position in which fluid flow to both outlets is blocked and a second position in which the first fluid outlet is open to flow, the piston physically blocking the outlet for the first fluid in the first position, a diaphragm attached to the piston and to the walls of the central chamber dividing the central chamber into first and second annular chambers surrounding the piston, the inlet and outlet for the first fluid being into and out of the first chamber and the inlet and outlet for the second fluid being into and out of the second chamber, movement of the piston from the first to the second position allowing flow of the first fluid through its outlet and causing movement of the diaphragm with the piston to reduce the volume of the second chamber to expel second fluid through its outlet and movement of the piston from the second position to a position intermediate the first and second positions causing an increase in volume of the second chamber whereby second fluid maybe sucked from a source thereof through its inlet into the second chamber.
It will be appreciated that the piston may then be reciprocated repeatedly between the second and intermediate positions to repeatedly reduce and increase the volume of the second chamber whereby second fluid may be pulsed through its outlet while the first fluid continues to flow. When sufficient fluids have been allowed to flow, e.g. to complete a beverage dispense, the piston is moved back to the first position and flow of both fluids stops.
In another aspect the invention provides a beverage dispenser comprising a valve of the invention, one inlet of which is connectable to a source of diluent, usually plain or carbonated water, and the other inlet of which is connectable to a source of concentrate, and a mixing nozzle into which both outlets of the valve lead and from which the mixed beverage is dispensed.
The inlet to the second chamber of the valve may contain a non-return suction valve openable into the second chamber when second fluid pressure in that chamber is reduced by the piston moving from the second to the intermediate position. Second fluid, e.g. a beverage concentrate, is then sucked into the second chamber and is then expelled from the second chamber through its outlet when the piston returns to the second position.
The outlet to the second chamber of the valve preferably contains a non-return valve that opens the outlet when a predetermined minimum pressure level of fluid in the second chamber is reached. Thus this non-return valve may be spring-assisted to provide the required minimum back pressure against flow or it maybe of a flexible construction designed to open when the required chamber pressure is reached.
It will be appreciated that when the piston has been moved from the first, closed position, the outlet for the first fluid, e.g. beverage diluent, remains fully open while the piston is reciprocated between the second and intermediate positions. The diluent, therefore, in a beverage dispense, has a nominal flow rate and a flow sensor may be provided in the concentrate flow line to match the required flow of concentrate to the flow of diluent. Preferably, a flow sensor may be provided in both flow lines, the sensor being connected to a pre-programmed controller to cut off flow when the required volumes have been dispensed.
The diluent flow into the first chamber may provide a pressure of, for example, 6 to 8 bar on its side of the diaphragm when the valve is closed. This pressure, therefore, provides assistance to the initial movement of the piston when the valve is opened and the piston moved from the first towards the second position. Similarly, the above-described back pressure provided by the second chamber outlet non-return valve reduces the pressure on the diaphragm during movement of the piston from the second towards the intermediate position.
By way of example only, for a typical syrup/diluent mixture for a beverage, the pumping frequency from the second chamber, i.e. the frequency of moving the piston from the second position to the intermediate position and back again may be from 5 to 15 pulses per minute, e.g. 10 per minute.
The means to move the piston is preferably controlled by the controller on receiving a dispense signal, e.g. the pressing of a button for a particular beverage. The controller will then open the valve by instructing a suitable actuator to move the piston to the second position and to reciprocate the piston between the second and intermediate positions for the time appropriate for the required flow for the size of beverage to be dispensed.
The actuator may conveniently be a stepper motor, e.g. of the pulsed, magnetically driven type, or a proportional solenoid actuator but other actuators, e.g. a lever mechanism or a diaphragm operated mechanism may be used if desired.
It will be appreciated that whatever actuator mechanism is used to move the piston, it must be designed to operate between the three basic piston positions, i.e. it must be able to move the piston to the first, valve closed position and to the second, valve open position and to reciprocate the piston between the second position and the intermediate position in which the first fluid outlet remains open.
The second fluid outlet may be provided with plenum means to even the pulsed flow from the second chamber outlet. Thus flow of concentrate, or other second fluid, into a discharge or mixing nozzle may be smoothed to improve mixing with the first fluid (diluent). This may be achieved by a variety of means. For example, the outlet may pass through or comprise a flexible chamber, which may be a spring-assisted diaphragm.
Where the second fluid is a concentrate, it may be supplied to the second chamber of the valve from a source of concentrate, e.g. a flexible bag positioned above the second fluid inlet. The concentrate from the bag cannot flow through the second chamber outlet except during pulsing of the diaphragm because of the back pressure applied at the non-return valve in the outlet. Thus, this arrangement prevents dripping of concentrate from the outlet when dispense is not required and the valve is closed.